The present invention relates to magnetic pole material for a composite thin-film magnetic head and a process for producing the same, as well as a composite thin-film magnetic head manufactured with the magnetic pole material and a magnetic recording device comprising such a magnetic head.
Magnetic heads mounted on a magnetic disk device are required to provide higher and steeper magnetic field for magnetic recording of higher density. More recent magnetic heads comprise both a magneto-resistance effect element for read of information and an inductive head element for recording of information. Such magnetic heads are typically referred to as a composite thin-film magnetic head and have been dominant in these days.
In the composite thin-film magnetic heads of the type described, magnetic material is used for an upper magnetic layer, or else both upper and lower magnetic layers, of the inductive head element and is required to have a high saturation magnetic flux density to provide a high magnetic field for writing. The magnetic material is also required to be excited easily as a result of flowing an electrical current through a write coil. Taking the above into consideration, it is necessary for the magnetic material for the composite thin-film magnetic heads to have a small coercive force and a high magnetic permeability. In other words, good soft magnetic material should be selected for this purpose.
An example of the magnetic material that meets the above requirements is a Ni--Fe (nickel--iron) alloy film called a permalloy. Among permalloy films of various formulations, one with approximately 82% nickel content is typically used as the magnetic material for the upper and the lower magnetic layers of the inductive head element because of its having a magnetostrictive constant of nearly equal to zero. Such a permalloy is hereinafter referred to as an "82% permalloy". The 82% permalloy has a saturation magnetic flux density of approximately 9,000-10,000 gauss. The good soft magnetic material having the higher saturation magnetic flux density can provide a magnetic head with a higher and steeper magnetic field for writing.
Various materials have been proposed as the soft magnetic material for the magnetic heads that have the higher saturation magnetic flux density than the 82% permalloy does. In particular, Co--Fe--Ni (cobalt--iron--nickel) ternary alloy films are of great concern because they have a small coercive force and a small magnetostrictive constant while allowing the saturation magnetic flux density of 14,000 gauss or higher. Thus, the Co--Fe--Ni ternary alloy films have been examined on their formulation and possible applications as additives.
However, conventional Co--Fe--Ni ternary alloy films usually have an iron content of 25% by weight or smaller. Such a ternary alloy film can provide the saturation magnetic flux density of 14,000-18,000 gauss at the highest. Higher saturation magnetic flux density cannot be obtained with the conventional Co--Fe--Ni ternary alloy films.
On the other hand, the magnetic material having the higher saturation magnetic flux density should be used for the upper or the lower magnetic layer in order to achieve recording at a higher density.